Gut bacteria convert choline and carnitine into TMA, which the liver oxidizes to TMAO, a contributor to atherosclerosis.

“in the people I work with who are on carnivore diets I have seen TMAO levels that are high and TMAO levels they're low right so it probably has to do with the gut flora and some of us have got microbes that make tma t ma from choline and carnitine but there are many studies I've seen which show or at least even anecdotes where vegans and vegetarians can have high levels of tma-2 TMAO as well”

“when you eat animal-based products that are rich in choline and carnitine certain gut bacteria convert the choline and carnitine to trimethylamine or tma which is then absorbed and oxidized in the liver to tmao”

“why would tmao be harmful for us when it's found in very high amounts in things like fish so trimethyl and oxide amine and oxide and seafood ah interesting tmao marker of seafood consumption if you read this paper you find that tmao in fish is actually higher on a gram per gram basis than the amount of tmao that would be formed if you ate meat from choline and carnitine”

“It is true that these compounds, carnitine and choline, get metabolized by gut microbiota and eventually form a compound called called trimethylamine, which is then metabolized via an enzyme in the liver called FMO, flavin monooxygenase, into trimethylamine oxide.”

“choline and carnitine found in meat eggs organs and milk are the precursors for tmao”

“TMAO is mostly known in being found naturally in fish and in being produced in the gut in very rare cases where there were people with genetic disorders and I don't even remember my head with those genetic disorders were but they were feeding them absolutely massive amounts of choline and so was known before that that in those cases of enormous choline loading some of that choline would be converted to trimethylamine by gut bacteria and that that trimethylamine and actually the the interest was largely in the trimethylamine because the trimethylamine is the more smelly compound so this would produce fish odor syndrome these people are smelling like fish so that was what was known about it at that point but then in 2011 I think was the first paper the Cleveland Clinic came out with experiments I think in first and mouse but also in humans showing well showing different things so in mice that were genetically engineered to have defects in their lipoprotein metabolism they showed that TMAO was directly atherogenic and in humans they showed that in there were two different papers the first one looked at choline and the second one looked at meat but what they were showing was that TMAO levels in humans corley with heart disease risk and when humans eat either choline or carnitine they will metabolize both of those two trimethylamine in the gut and the liver will convert it to TMAO”

“if I recall there were basically three ways that they were suggesting you could get too much of it one was too much fish if you eat fish you're getting the TMI don't they mention fish maybe I'm confusing it with a different paper but I thought one argument was too much fish is too much TMAO too much carnitine which is found in sports drinks is going to be converted and too much choline so basically any of those three that were too many were problematic”